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Epidemiology of sudden infant death in North Carolina: do cases tend to cluster?

Cr^ NORTH CAROLINA STATE LIBRARY N. C.
^^f/ji:/^ RALEIGH Doc.
DEC PHSB STUDIES
A Special Report Series by the N.C. Department of Human Resources, Division of
Health Services, Public Health Statistics Branch, P.O. Box 2091, Raleigh, N.C.
No. 16 December 1979
EPIDEMIOLOGY OF SUDDEN INFANT
DEATH IN NORTH CAROLINA:
Vo Coii>e.i> Te.nd to Cla^tdfL?
In the last decade, sudden infant death syndrome (SIDS) has become widely
recognized as the leading category of postneonatal deaths, that is, deaths to children
28 days to one year of age. It occurs at a rate of two to three per 1,000 live births
(3,6,9,11,15) and is responsible for approximately 160 to 180 deaths each year in
North Carol i na.
Many theories have been proposed to explain the etiology of SIDS. Proposed
causative agents, ranging from viral agents and infectious diseases to simple
climactic changes, have been listed by Beckwith (l).
Several epidemiologic studies have suggested that SIDS deaths tend to cluster,
especially seasonally (1,5"7,18). Beyond this, no known published reports in the
United States have shown statistically whether SIDS deaths actually do cluster in
certain time and space dimensions. In fact, a study by Froggatt, et al. (6) in
Northern Ireland is the only known published report to statistically examine the
question of clustering, and that study was done before a specific SIDS code was
developed in 197'*-
With the present availability of SIDS data by county, the question of cluster-ing
of SIDS deaths in North Carolina is addressed. In particular, the purpose of this
report is threefold: (a) to describe the epidemiology of SIDS cases occurring in
North Carolina, (b) to test the null hypothesis that SIDS occur randomly throughout
the state, that is, that no apparent clustering of SIDS exists in North Carolina and
(c) to describe the time and space parameters which adequately portray the clusters
if the null hypothesis is rejected.
A second component of this study involves examining SIDS cases on the Medical
Examiner's (ME) files and the Vital Statistics (VS) files. The purpose here is to
determine the extent to which the two files disagree and to provide explanations for
the differences. This component is important because results provide the basis for
determining which record system to use.
Ascertainment of SIDS Cases
The Office of the Chief Medical Examiner is charged with investigating and
certifying all deaths due to violent, unusual or unidentified causes. These
investigations are carried out through a statewide system of regional pathologists
and licensed county medical examiners. In the case of apparent SIDS, an autopsy is
required to document that no specific underlying cause of death can be determined.
Through normal death registration channels, the Vital Records Branch of the
Division of Health Services receives death certificates for SIDS cases. Almost
always, these should be the same as cases reported to the Medical Examiner System;
however, discrepancies were found when infant deaths on the two computerized files
were matched, using 197^* and 1977 as test years. Discrepancies involved the follow-ing
:
7 1979

Cr^ NORTH CAROLINA STATE LIBRARY N. C.
^^f/ji:/^ RALEIGH Doc.
DEC PHSB STUDIES
A Special Report Series by the N.C. Department of Human Resources, Division of
Health Services, Public Health Statistics Branch, P.O. Box 2091, Raleigh, N.C.
No. 16 December 1979
EPIDEMIOLOGY OF SUDDEN INFANT
DEATH IN NORTH CAROLINA:
Vo Coii>e.i> Te.nd to Cla^tdfL?
In the last decade, sudden infant death syndrome (SIDS) has become widely
recognized as the leading category of postneonatal deaths, that is, deaths to children
28 days to one year of age. It occurs at a rate of two to three per 1,000 live births
(3,6,9,11,15) and is responsible for approximately 160 to 180 deaths each year in
North Carol i na.
Many theories have been proposed to explain the etiology of SIDS. Proposed
causative agents, ranging from viral agents and infectious diseases to simple
climactic changes, have been listed by Beckwith (l).
Several epidemiologic studies have suggested that SIDS deaths tend to cluster,
especially seasonally (1,5"7,18). Beyond this, no known published reports in the
United States have shown statistically whether SIDS deaths actually do cluster in
certain time and space dimensions. In fact, a study by Froggatt, et al. (6) in
Northern Ireland is the only known published report to statistically examine the
question of clustering, and that study was done before a specific SIDS code was
developed in 197'*-
With the present availability of SIDS data by county, the question of cluster-ing
of SIDS deaths in North Carolina is addressed. In particular, the purpose of this
report is threefold: (a) to describe the epidemiology of SIDS cases occurring in
North Carolina, (b) to test the null hypothesis that SIDS occur randomly throughout
the state, that is, that no apparent clustering of SIDS exists in North Carolina and
(c) to describe the time and space parameters which adequately portray the clusters
if the null hypothesis is rejected.
A second component of this study involves examining SIDS cases on the Medical
Examiner's (ME) files and the Vital Statistics (VS) files. The purpose here is to
determine the extent to which the two files disagree and to provide explanations for
the differences. This component is important because results provide the basis for
determining which record system to use.
Ascertainment of SIDS Cases
The Office of the Chief Medical Examiner is charged with investigating and
certifying all deaths due to violent, unusual or unidentified causes. These
investigations are carried out through a statewide system of regional pathologists
and licensed county medical examiners. In the case of apparent SIDS, an autopsy is
required to document that no specific underlying cause of death can be determined.
Through normal death registration channels, the Vital Records Branch of the
Division of Health Services receives death certificates for SIDS cases. Almost
always, these should be the same as cases reported to the Medical Examiner System;
however, discrepancies were found when infant deaths on the two computerized files
were matched, using 197^* and 1977 as test years. Discrepancies involved the follow-ing
:
7 1979